Vitamin D For Dummies
Overview
Your plain-English guide to the many benefits of Vitamin D
Vitamin D is in the news every day, as new tests and studies reveal encouraging information about its power in maintaining good health and preventing major illnesses. No longer thought to just play a role in calcium intake and bone growth, Vitamin D has a host of other functions in the body, playing a role in prevention of serious diseases, including cancer, diabetes, and heart disease, as well as boosting immunity, improving athletic performance, losing weight, and more.
This hands-on,
plain-English guide is perfect for anyone looking for helpful advice and information on the "nutrient of the decade."
- Coverage of how Vitamin D works, and how much is needed for disease prevention
- How and where to get sufficient amounts of the right kind of Vitamin D – from both your diet and nutritional supplements
- The best ways to maintain healthy levels of Vitamin D
If you're looking to learn more about the many benefits Vitamin D can have on you and your family, you'll find everything you need right here.
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About The Author
Alan L. Rubin, MD has been a physician in private practice for more than 30 years. He is the author of several bestselling health titles, including Diabetes For Dummies, High Blood Pressure For Dummies, and Thyroid For Dummies.
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vitamin d for dummies
CHEAT SHEET
Vitamin D is essential for good health; however, it is a required nutrient only when you don't get enough ultraviolet B (UVB) rays from the sun. Unfortunately, many people can't get enough sun exposure and need to get vitamin D from their diet or from supplements. When you have enough vitamin D in your body, you can protect the health of your bones and prevent osteoporosis.
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Even before we knew what vitamin D was, we’ve understood that it is important for building strong bones. Bone isn’t an inert organ. It has critical functions in the body, which can be divided into three main categories: mechanical, synthetic, and metabolic.
Mechanical: Bone provides the mechanical functions of movement, protection (of major organs), shape, and sound transmission (in the inner ear).
Vitamins & Supplements
Some studies suggest that maintaining high vitamin D status may be important for protection from type 2 diabetes. Type 2 diabetes is 20 times more common than type 1 diabetes, and the incidence is rising at an alarming rate as the population becomes heavier and more sedentary.
Even in a person who seems destined to develop type 2 diabetes because of family history, it’s possible to hold off or prevent the disease by maintaining a normal weight, eating properly, and doing plenty of physical exercise.
Vitamins & Supplements
Your body typically adapts well to changing levels of dietary calcium. In relatively rare instances, however, your serum calcium levels may become too high or too low. Keep in mind that most adults need a calcium intake in the range of 1,000 to 1,500 mg per day.
When calcium intake is high, perhaps only more than 2,000 mg a day, this may gradually cause calcification of arteries and increase the risk of heart attack and stroke.
Doctors diagnose osteoporosis by performing a bone densitometry test, which measures the amount of mineral per square centimeter of bone. The areas studied in a bone densitometry study are usually the lumbar spine and the upper part of the hip. The test takes about ten minutes to complete.
The bone density correlates fairly well with the tendency of a bone to fracture.
Vitamins & Supplements
Recent studies suggest that vitamin D may play a role in brain development and brain health from birth to old age. Interesting new associations link high vitamin D status to the prevention of certain psychiatric conditions and in the development of Alzheimer’s disease.
Vitamin D may play a role in various developmental stages and disease states, including autism, Alzheimer’s disease, Parkinson’s disease, depression, and seasonal affective disorder.
Vitamins & Supplements
Studies suggest that vitamin D may play a role in preventing and treating diabetes. Type 1 diabetes is an autoimmune disease that results from destruction of the insulin-producing beta cells of the pancreas. Insulin is the key hormone that controls the blood glucose (sugar) levels. Without insulin, glucose doesn’t enter the cells that make up your muscles and blood glucose levels rise, especially after you eat a meal.
Vitamins & Supplements
Women should ensure that they have a satisfactory level of vitamin D both before and during pregnancy. Pregnant adult women and nursing mothers need 600 IU of vitamin D every day, and teen mothers need 800 IU daily.
During pregnancy, a woman is eating for two. The growing fetus gets its nutrition entirely from the mother.
Vitamins & Supplements
If you're heard or read about the advantages of making vitamin D from the sun, you may be ready to grab your towel and head to the nearest pool or beach for a few hours of sun worship. Not so fast. Chances are that you need to spend less than 30 minutes in the sun to give your body enough time to generate the vitamin D you need.
Vitamins & Supplements
If you want to optimize your vitamin D levels, you'll need to know how much vitamin D you need in your diet to get there. You can get vitamin D from your diet and also after the sun stimulates your skin to make vitamin D. The best way to know for certain whether you have enough vitamin D in your body is to get a specific blood test that measures 25-hydroxyvitamin D.
The medical community has known of the benefits of vitamin D on bone health for decades. In recent years, scientists have discovered that vitamin D may play a role in many other aspects of our health. This overview provides a look at some areas in which vitamin D may improve health and prevent diseases.
Building bone with vitamin D
The work of calcitriol (active vitamin D) is intimately linked to the way your body uses calcium.
Over the last 30 years, evidence has accumulated that shows higher vitamin D status intake or higher 25-hydroxyvitamin D levels may prevent cancer. Since 1980, 16 different cancers have been shown to be associated with low vitamin D!
Studies in cultured cells done with calcitriol (active vitamin D) show that it may affect cancer in numerous ways.
Vitamins & Supplements
A lot of interesting research points to an important role for vitamin D (more specifically, calcitriol) in the body's immune system. Most of this research has been done in cultured cells (cells isolated from the body and grown in special solutions of nutrients) and in animals with either severe vitamin D deficiency or whose genes have been altered to “knock out” proteins that control vitamin D metabolism or active vitamin D action.
Teeth aren’t exactly bones, but they’re made up of similar tissues and are subject to the same problems bones may have. Vitamin D deficiency, including the conditions of rickets and osteomalacia, also can affect teeth.
Exploring the normal development of teeth
Humans develop two different sets of teeth:
The baby, or primary, teeth begin to erupt from the gums at six months of age, which any parent knows is a painful time called teething.
Vitamins & Supplements
Evidence shows that heart failure is associated with low blood levels of vitamin D. When a person suffers from heart failure, the heart is unable to pump enough blood to supply the needs of the body. Heart failure is a relatively common condition in the elderly population over age 65, occurring in up to 10 percent of people in that age group.
Vitamins & Supplements
Prostate cancer is the most common cancer in men in the United States. Some scientists think vitamin D may help protect against prostate cancer. Prostate cancer generally occurs in men over the age of 50; however, it is slow growing in most men and takes a lifetime to develop.
Prostate cancer has been found in the prostate gland of more than 80 percent of men over the age of 70 who died from an entirely unrelated disease.
If you want to know whether you have enough vitamin D in your body, you must have a blood test for 25-hydroxyvitamin D. Depending on where you live, you may have trouble convincing your doctor to order a vitamin D test for you. Because of the high demand over the past few years, the test is no longer covered in some parts of the U.
Vitamins & Supplements
Most healthy adults need 600 or 800 IU of vitamin D per day. That means you can choose to take a multivitamin and mineral supplement that has this amount in it, you can take a combined vitamin D and calcium supplement, or you can take a dedicated vitamin D supplement.
Deciding what form of vitamin D to take
If you focus only on the bottles of vitamin D supplements at your local drug store, you may see several choices among that one vitamin.
Vitamins & Supplements
If you have dietary restrictions or you have a condition that reduces your ability to absorb vitamin D, you can still get plenty of vitamin D. How, you ask? From the sun, of course. But suppose that you live at the latitude of San Francisco (37 degrees north latitude) or above, and it’s winter. You can’t get enough vitamin D from the sun at that latitude in the winter.
Vitamins & Supplements
Many of the best sources of calcium are also good sources of vitamin D, especially dairy foods such as milk, yogurt, and cheese. Other good sources are fortified cereals, tofu processed with calcium, enriched farina, almonds, dried beans, and soybeans.
The table lists the best sources of calcium to include in your diet.
Vitamins & Supplements
Taking a vitamin D supplement correctly is easy. You simply need to have the right dose (usually in the form of a gel capsule), pop it into your mouth, and swallow it with a little water. That’s all there is to it. No advantage is gained by taking a vitamin D supplement several times daily over taking one capsule once a day.
Vitamins & Supplements
Skin production of vitamin D from exposure to the sun improves the condition of psoriasis — an autoimmune skin disease that consists of red, scaly patches that have a silvery-white appearance. This is using vitamin D as therapy, not for prevention; however, there’s no evidence that you can take large amounts of vitamin D as a pill and get the same benefits as UV light or a topical form of vitamin D.
Vitamins & Supplements
More than one in three Americans has heart disease or suffers from a condition that increases the risk of getting a cardiovascular disease. Vitamin D may play a significant role in many aspects of heart and vascular health.
The numbers of people affected by heart disease are staggering and include the following:
High blood pressure: 75 million
Heart attacks: 8.
Vitamins & Supplements
Much more investigation is necessary before the role of vitamin D in fibromyalgia, if there is one, is established. Fibromyalgia is a chronic condition associated with pain in the muscles and bones, as well as any of the following signs and symptoms:
Fatigue
Joint stiffness
Lack of abnormal diagnostic tests
Lack of abnormalities on physical examination
Sleep disturbance
The lack of abnormalities results in confusion over whether this is a disease or a psychiatric condition.
Vitamins & Supplements
Even as researchers continue to discover how vitamin D can protect your health, a lot of misinformation still surrounds this amazing vitamin. Here are some of the key points you need to know to understand the role of vitamin D in your health.
You can make vitamin D in your skin when you're exposed to UVB light from the sun.
Some evidence suggests that vitamin D may play a role in preventing asthma. Asthma is a common condition in the United States and throughout the world. Seven percent of Americans, about 22 million people, suffer from asthma. A third of them are children. Asthma can be severe but, fortunately, deaths from asthma amount to only about 3,450 per year.
Vitamins & Supplements
High blood pressure is exceedingly common in the United States, occurring in one of every four people, or 75 million Americans. Vitamin D may be used to help prevent or treat high blood pressure. Only three-fourths of those who have high blood pressure are aware of their condition.
High blood pressure is a chronic medical condition discovered by measuring the pressure in one or more arteries, usually the brachial artery in the arm just below the shoulder.
Vitamins & Supplements
The U.S. Government has provided guidelines on calcium intake — Recommended Dietary Allowances (RDA) — based on age group (and gender, for those in the 51-70 age group). Because your body doesn’t make minerals such as calcium, you need to eat foods rich in calcium for optimal health.
As with other nutrients that you consume, expert panels of scientists determine the acceptable level of calcium intake for optimal health.
In our increasingly overweight society, weight management has become an important concern. Substantial information suggests that vitamin D plays a role in fat cell biology and that this may relate to weight loss and weight management.
Fat ties up vitamin D. If an overweight person and a normal-weight person take the same amount of vitamin D, the blood level of vitamin D in the normal-weight person goes higher than in the overweight person.
Osteoporosis is a brittle bone disease in which both the structure of the bone and its mineralization are reduced. Vitamin D deficiency may be a risk factor, especially for women. People with osteoporosis are more likely to experience a bone fracture sometime in their life.
Osteoporosis is the most common bone disease, occurring in one of every three women over age 50.
Vitamins & Supplements
Adequate levels of vitamin D may control or prevent coronary artery disease, high blood pressure, and heart failure. A heart attack may result when these conditions aren’t treated. Researchers are trying to determine whether vitamin D can prevent heart attacks and, if so, how much vitamin D is needed. They are also curious to learn what vitamin D can do after a person has a heart attack.
New recommendations for vitamin D were released by an expert panel in 2010. These recommendations for daily intake of vitamin D are based on the current literature on vitamin D and are set to protect the health of your bones. They're based on the assumption that you get no vitamin D from sun exposure.
2010 Recommendations for Intake of Vitamin D
Age
RDA or AI*
UL**
Birth to 6 months
400 IU***
1000 IU
7–12 months
400 IU
1500 IU
1–3 years
600 IU
2500 IU
4–8 years
600 IU
3000 IU
9–70 years
600 IU
4000 IU
More than 70 years
800 IU
4000 IU
*RDA = recommended daily allowance; AI = adequate intake**UL = upper safe limit for daily intake***IU = International Units
Some people believe that you may need even more vitamin D than these recommendations; however, the scientific evidence to support these claims is lacking.
Vitamins & Supplements
You might think that you'd be able to get enough vitamin D by eating animals and plants that are rich food sources of vitamin D; however, it’s not that simple. With rare exceptions, the vast majority of foods don’t have enough concentrated vitamin D to get you to 600 or 800 IU per day.
Scientists have tried to “fortify” certain foods by adding more vitamin D.
Vitamins & Supplements
As many as 70 percent of people age 70 and older have inadequate levels of 25-hydroxyvitamin D. They also tend to have low vitamin D levels all year long; they don’t get the summer boost from the sun. The elderly are deficient in vitamin D for these reasons:
Decreased ability to make vitamin D due to changes in their skin
Tendency to avoid the sun or live in places where they get less access to sun (such as nursing homes)
Diminished exposure to foods that contain vitamin D
Decreased memory, leading to failure to take vitamin D supplements
Some evidence that intestinal absorption of vitamin D is reduced in the elderly
Although testing the blood level of 25-hydroxyvitamin D is the only way to know for certain if someone is getting enough vitamin D, the 800 IU per day recommended by the Institute of Medicine should be sufficient for most elderly (unless the person has a problem with intestinal absorption of vitamin D, due to a previous surgery, celiac disease, and so on).
Vitamins & Supplements
Some researchers think there is a link between vitamin D levels and coronary artery disease (CAD). CAD is the term for the type of cardiovascular disease with progressive closing of arteries that supply blood to the heart. It’s also known as atherosclerotic heart disease or atherosclerosis. If a critical artery closes completely, the result is a myocardial infarction, or heart attack.
Vitamins & Supplements
Of all the cancers proposed to have a relationship to vitamin D, perhaps colon cancer has the strongest connection. More properly called colorectal cancer because the disease may involve any part of the large intestine, including the rectum, colorectal cancer can be picked up in early and curable stages with proper screening.
Vitamins & Supplements
Vitamin D may have a role in boosting the immune system and helping your body fight off nasty infections such as the flu and tuberculosis. Many books have been written about the positive effect of sunlight on these and other infectious diseases. These diseases are caused by viruses, bacteria, and other tiny organisms that enter the body through the lungs, the skin, or the intestines.
Vitamins & Supplements
Graves’ disease is an autoimmune disease in which the body’s metabolism speeds up. It's possible that vitamin D deficiency may play a role in the development of Graves' disease — there is some evidence to suggest this, but it's not yet proven.
Graves’ disease is caused by an antibody that makes the thyroid gland produce too much thyroid hormone — the antibody activates the thyroid stimulating hormone (TSH) receptor.
Systemic lupus erythematosis, often shortened to just lupus, is an autoimmune disease of the connective tissues that support and protect organs. Vitamin D deficiency may play a role in the development and progression of lupus, but this hasn't been proven yet.
Lupus can affect every organ in the body because connective tissue surrounds all organs.
Vitamins & Supplements
Multiple sclerosis (MS) is an autoimmune disease that attacks a person’s own nervous system. Vitamin D deficiency may play a role in the onset and progression of multiple sclerosis. In MS, the myelin sheaths that surround the nerves in the brain and spinal cord are damaged.
Just like the wires in your house can’t transmit properly if they’ve lost their surrounding insulation, so too the nerves can’t conduct an electrical signal without their myelin sheaths, and the function of that nerve is lost.
Vitamins & Supplements
Lung cancer is the most common deadly cancer among both men and women. Studies suggest that normal vitamin D levels may help prevent lung cancer. In the United States in 2009, about 220,000 new cases of lung cancer were diagnosed. That same year, about 153,000 people died of lung cancer. People over age 65 are mostly affected.
Vitamins & Supplements
Ovarian cancer may arise in the ovaries, oval-shaped organs found in pairs in the female reproductive system. Studies suggest that vitamin D plays a role in preventing and treating ovarian carcinoma. In 2009, about 21,550 cases were diagnosed and 14,600 women died of ovarian cancer in the United States. Ovarian cancer is usually a cancer of women older than age 60.
Vitamins & Supplements
Pancreatic cancer generally has a poor prognosis because of its location in relation to other critical organs. Studies suggest that vitamin D may play an important role in fending off pancreatic cancer. The pancreas has two major functions:
Producing hormones, insulin, glucagon, and somatostatin to control the glucose (sugar) in the body
Producing enzymes that go into the small intestine and help to break down food into particles that the body can absorb
Most of the pancreas lies behind the stomach, as shown in the following diagram.
Vitamins & Supplements
Rheumatoid arthritis (RA) is an autoimmune disease that affects the synovial joints between bones. Vitamin D intake may modulate RA, because calcitriol modulates the adaptive immune system. Like all autoimmune diseases, rheumatoid arthritis is caused by the adaptive immune system.
RA can affect the main synovial joints of the body:
Elbow joints
Finger and toe joints
Hip joints
Knee joints
Shoulder joints
Wrist joints
The synovial joints are surrounded by a joint capsule.
Vitamins & Supplements
Breast cancer is the most commonly diagnosed cancer in women in the United States after skin cancer. Some studies show that avoiding vitamin D deficiency may help to limit your risk of breast cancer. About 250,000 new cases of breast cancer were diagnosed in 2009, and about 40,000 deaths resulted from breast cancer.
Vitamins & Supplements
Vitamin D may play a role in several brain disorders that cause depression, so is it any surprise that people have looked for a role for vitamin D in depression? Depression, which psychiatrists officially call major depressive disorder, is a mood disorder that varies greatly in its prevalence and severity. Using a broad definition of depression, about 4 percent of men and 8 percent of women will have depression over the course of a year.
Vitamin D is essential for good health; however, it is a required nutrient only when you don't get enough ultraviolet B (UVB) rays from the sun. Unfortunately, many people can't get enough sun exposure and need to get vitamin D from their diet or from supplements. When you have enough vitamin D in your body, you can protect the health of your bones and prevent osteoporosis.
Vitamins & Supplements
Overdosing on vitamin D isn’t easy, but it is possible if you’re taking supplements. In contrast, your body doesn’t allow overdosing from the sun alone. When your vitamin D levels reach a high, potentially toxic level, your skin stops allowing the production of vitamin D.
You can get vitamin D intoxication if you take a very large dose for a prolonged period of time, or a huge dose for a short period of time.
Vitamins & Supplements
When seniors comply with their recommended calcium intake and their vitamin D levels are sufficient, bone fracture risk is significantly reduced compared to seniors who don’t get enough calcium or have vitamin D deficiency. Even when vitamin D is sufficient, it’s essential that seniors get enough calcium in their diet.
Vitamins & Supplements
Adequate levels of vitamin D are essential for children before birth, after birth, and throughout childhood to ensure the proper development of bones and teeth. If they get enough vitamin D throughout childhood, they may avoid problems in adulthood, such as osteoporosis.
The recommended optimal level of 25-hydroxyvitamin D in children is the same as in adults — 20 ng/ml (50 nmol/L).
New information about vitamin D's role in health is being published almost daily. Here are the key functions of vitamin D, divided into those that are firmly established, those for which there is growing evidence, and those that are proposed but not yet confirmed.
It's firmly established that vitamin D
Facili
Vitamins & Supplements
Calcium is tightly linked to many of the roles that vitamin D plays in the body. In bone health (and other physiologic systems), calcium is a key player. Calcium is a mineral that must be constantly eaten to build bone and maintain the blood level of calcium.
When people hear about calcium, they think “bone.” Bone is formed by special cells in the body.
Vitamins & Supplements
Outside the body, vitamin D comes from three major sources: the sun, food, and supplements. Sunlight is considered to be the best source of vitamin D for your body, followed by foods that contain vitamin D, and finally, vitamin D supplements.
Vitamin D from the sun
The sun has provided vitamin D for thousands of years.
Vitamins & Supplements
Although a newborn baby doesn’t need as much vitamin D as required by the pregnant or nursing mother, she continues to need sufficient vitamin D. Bones, organs, and critical structures in the brain are developing, and sufficient vitamin D appears to be essential to growth and development.
There’s no doubt that children born with a vitamin D deficiency won’t reach their full height or bone density because of the important role vitamin D plays in calcium metabolism — these conditions will affect them throughout their lives.
Vitamins & Supplements
Many people don’t have enough vitamin D, and are unaware of its many benefits. Scientists are discovering new possible roles for this important nutrient almost daily. If you think you have enough vitamin D in your body, you may be in for a surprise.
What is vitamin D?
A vitamin is defined as an essential nutrient that a living being must acquire in tiny amounts from the diet.
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